… async IO mode. There are two reasons for that. First, MySQL/InnoDB uses async writes, so this will emulate database load… do a wild guess about drops – the drive periodically cleans an internal cache or something. To understand better what kind of response… you are interested more in SSD and MySQL questions – I will be giving a webinary “MySQL and SSD” on May-9. It…
Post: Troubleshooting MySQL Memory Usage
March 21, 2012 By 3 Comments
… Check for Table Cache Related Allocations There are cases when MySQL will allocate a lot of memory for table cache, especially if you…) are all connection buffers and so if you close connection MySQL can clean them up. Killing connections (or stopping related applications) and… and fixed. This is where your MySQL Support contract can be handy. Conclusion Understanding where MySQL can allocate memory can help us…
Post: Query Profiling with MySQL: Bypassing caches
September 12, 2007 By 6 Comments
… simple – because SQL_NO_CACHE only bypasses query cache but it has no change on other caches, which are MySQL Caches – Innodb Buffer Pool and… caches? For MySQL Caches you can restart MySQL and this is the only way to clean all of the caches. You can do FLUSH TABLES to clean MySQL table cache…
Post: Getting real life query speeds with MySQL
January 10, 2007 By 10 Comments
… kind of other caches and QueryCache is only first in line. There is also all kinds of page caches inside MySQL (key_buffer and innodb_buffer_pool_size) which can be cleared by MySQL restart. Even if you restart MySQL server… makes sense. In this case you would want to clean MySQL and OS caches, most simple way being to restart OS (there are…
Post: Aligning IO on a hard disk RAID – the Benchmarks
June 9, 2011 By 11 Comments
… make sure caches were clean. OLTP benchmark As the goal was to compare performance with different IO alignment, not different MySQL configurations, I didn’t try out different MySQL versions or settings. Moreover, I have…
Post: Caching techinques
August 8, 2006 By 11 Comments
…. Cache Invalidate With this apporach you invalidate or remove objects in cache once underlying information is updated. This is how MySQL Query Cache works… of what has to be invalidated – approach used by MySQL Query Cache is too coarse invalidating a lot of queries which really… this approach is – you cache operations have constant complexity – you do not have to do big invalidation clean up on updates. Let…
Post: MySQL Crash Recovery
July 30, 2006 By 26 Comments
… only problem as we’ll see. MySQL has angel process mysqld_safe which will restart MySQL Server in most cases. It is… unsync with internal Innodb dictionary may cause MySQL to fail with wierd error messages. In MySQL 4.1 sync_frm option was… – If you restart MySQL server its caches (key_buffer, innodb_buffer_pool, query_cache,table_cache) are cleaned, so may be OS caches. This may reduce…
Post: The MySQL optimizer, the OS cache, and sequential versus random I/O
April 28, 2008 By 17 Comments
… whether a read will be satisfied from the operating system cache, or whether it’ll have to go to disk. (This… omit the details and keep this clean. Let’s take a look at the tables. mysql> show table status like ‘fact’\G… about the OS cache. This is why an expert is sometimes needed to provide the missing information. If the MySQL optimizer were…
Post: Percona Server 5.1.58-12.9
August 17, 2011 By 2 Comments
… and has been removed (buf_LRU_insert_zip_clean). Bugs Fixed: #802825 / #61341 in MySQL (Yasufumi Kinoshita). Compatibility Collations Two new collations…/restore here. Bug Fixes When adding a table to the cache, the server may evict and close another if the table… Slave SQL thread. Bugs Fixed #813587 / #51196 and #61790 in MySQL (Alexey Kopytov). Uninitialized values in the Slow Query Log patch…
Post: The two even more fundamental performance metrics
May 5, 2011 By 6 Comments
… throw away part of the data set to clean it up for modeling. Plot arrivals versus completions. …, maybe a bit longer. This is common in MySQL servers I work with when they’re running …What probably happened here was something like a small cache stampede. The application sent a burst of extra queries…
